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On Friday 18 Sep 2015 19:30:49 Rich Freeman wrote: |
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> On Fri, Sep 18, 2015 at 2:19 PM, Mick <michaelkintzios@×××××.com> wrote: |
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> > On Friday 18 Sep 2015 19:15:50 Rich Freeman wrote: |
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> >> On Fri, Sep 18, 2015 at 1:56 PM, Mick <michaelkintzios@×××××.com> wrote: |
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> >> > On Friday 18 Sep 2015 17:16:54 Marc Joliet wrote: |
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> >> >> On Friday 18 September 2015 10:31:01 Mick wrote: |
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> >> >> >A couple of months ago the akonadi DB went sideways and kmail played |
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> >> >> >up as a result. Again I was suspicious of btrfs, but neither the |
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> >> >> >logs nor fsck showed up anything. |
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> >> >> |
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> >> >> I take it "btrfs scrub" didn't turn up anything, or is that what you |
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> >> >> meant by fsck? |
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> >> > |
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> >> > Am I supposed to run scrub with I do not have a RAID running? I |
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> >> > thought scrub was meant for comparing checksums between mirrored fs - |
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> >> > have I got this wrong? |
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> >> |
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> >> You can actually run scrub on a non-raid btrfs setup. Btrfs will |
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> >> report any errors that it detects (using the checksumming in the |
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> >> filesystem), but it would not be able to fix errors unless you have it |
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> >> storing redundant data somewhere (even on non-raid it still stores |
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> >> redundant metadata by default, and you can choose to do this with data |
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> >> as well which protects against block-level failures but not disk-level |
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> >> failures, obviously). |
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> >> |
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> >> However, you'd have gotten the same errors in dmesg just trying to |
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> >> read the files - btrfs checks the checksum on all file read |
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> >> operations. That is a big part of the value of both btrfs and zfs. |
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> > |
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> > Ah! V interesting ... can I run scrub with mounted partitions, or do I |
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> > have to do it from a LiveCD? |
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> |
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> I didn't check, but I suspect you can only run scrub on a mounted |
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> partition. I also suspect that fsck probably has an option to do |
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> something equivalent offline. |
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> |
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> You do get the error-detection anyway just by reading files, and if |
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> you just ran find on your filesystem and catted every file you have to |
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> /dev/null that would actually accomplish the same thing as long as |
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> you're not in a redundant mode (simply reading all the files doesn't |
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> guarantee that all copies of each file are checked). |
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> |
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> The main reason for doing a scrub is to detect latent issues, and if |
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> you have redundancy that means you can auto-correct them today, rather |
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> than discovering them a month from now when the drive containing the |
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> only good copy fails. Even if you don't have redundancy maybe you |
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> rotate your backups every 30 days and detecting the error might mean |
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> having the ability to go back and restore a good copy of the file |
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> before it is completely replaced with bad copies. |
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|
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Thank you Rich, I ran 'btrfs scrub start /" and it found zero problems. dmesg |
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and syslog clean too. |
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-- |
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Regards, |
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Mick |
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